Presentation on theme: "The Fishes: Vertebrate Success in Water"— Presentation transcript:
1The Fishes: Vertebrate Success in Water Chapter 18Chapter 18
2Fish vs. Fishes “The ocean is full of fishes.” “Fish” refers to one or more individuals of one species; “fishes” refers to more than one species.“The ocean is full of fishes.”“This tank is full of fish.”
4Evolutionary Evidence Hagfish are the most primitive living craniates.2 Key craniate characteristics is: the brain and bone530 million years ago possible fossil with brain500 million years ago bone well developed in group of fishes called Ostracoderms (bony armor)Ostracoderms: The First Vertebrates (PA-18) The first vertebrates were fishlike animals that appeared more than 500 million years ago. The internal skeletons of these jawless creatures were cartilaginous and rarely preserved. Ostracoderms had bony external shields that covered the head and most of the trunk.From 3 to 10 inches long, ostracoderms had rather thick, flattened bodies with only a pair of side flaps to help in steering. They probably swam clumsily just above the sea floor. The mouth served to obtain oxygen and to retain bits of food.After true fish appeared about 400 million years ago, most ostracoderms rapidly became extinct. An armorless type survived, giving rise to modern lampreys and hagfish. Some ostracoderm plates are found in Devonian bone beds in Indiana.The first vertebrates were fishlike animals that appeared more than 500 million years ago. The internal skeletons of these jawless creatures were cartilaginous and rarely preserved. Ostracoderms had bony external shields that covered the head and most of the trunk.
5Evolutionary Evidence First vertebrates probably marineVertebrates did adapt to freshwater and much of the evolution of fish occurred there.Early vertebrate evolution involved the movement of fishes back and forth between marine and freshwater environments.
6Evolutionary Evidence The importance of freshwater in the evolution of fishes is evidenced by the fact that over 41% of all fish species are found in freshwater, even though freshwater habitats represent only a small percentage (0.0093% by volume) of the earth’s water resources.
7Subphylum Hyperotreti The HagfishHead-supported by cartilaginous barsBrain- enclosed in fibrous sheathIntro video to Hagfish
8Subphylum Hyperotreti Lack vertebraeRetain notochord (axial supportive structure)4 pairs of sensory tentacles surrounding their mouthsVentrolateral slime glandsSee the copious amounts of slimeSee hagfish make a knot
9Subphylum Hyperotreti Found: cold water marine habitatsFeed on: soft bodied invertebrates or scavenge on dead or dying fishTo provide leverage, the hagfish ties a knot in its tail and passes it forward to press against the preyEating on dead whale carcass
10Subphylum VertebrataVertebrae that surrounds a nerve cord and serves as the primary axial supportMost are vertebrates are members of the superclass GnathostomataJawed fishesTetrapods
11OstracodermsExtinct agnathans (without jaws) that belong to several classes.Bottom dwellers and very sluggishFilter feedersBony armorBony plates around mouth to act like a jaw
13Class Cephalaspidomorphi Live in both marine and freshwaterLarva filter feedersAdults prey on fishMouth –suckerlike with lips for attachment functions
14Class Cephalaspidomorphi Attach to prey with lips and teethUse tongues to rasp away scales
15Class Cephalaspidomorphi Salivary glands with anticoagulant; feed on blood
16Class Cephalaspidomorphi Two types:Freshwater brook lampreysFreshwaterLarval stage can last three yearsAdults only reproduce, never leave stream, then die
17Class Cephalaspidomorphi Two types:Sea lampreyLive in ocean or Great lakesEnd of life, migrate to freshwater stream to spawnFemale attaches to a stone with mouthMale uses his mouth and attaches to female’s headEggs are shedFertilization is external
31Class Chondrichthyes Chondro- cartilage, ichthyes- fish Sharks, skates, rays, ratfishCarnivores or scavengersMost marine
32Class Chondrichthyes Biting mouthparts Paired appendages Placoid scales (gives skin tough, sandpaper texture)Cartilaginous endoskeletonThese sharply pointed placoid scales are also known as dermal teeth or denticles. They give the shark’s skin the feel of sandpaper. The tip of each scale is made of dentine overlayed with dental enamel. The lower part of each scale is made of bone. The scales disrupt turbulence over the skin, considerably reducing the drag on the shark as it swims.Dried shark skin has been used for sandpaper!
35Subclass Elasmobranchii Shark teeth are modified placoid scalesRows of teethAs outer teeth wear out, newer teeth move into position from inside jaw and replaces themHow manyteeth do sharks have?
36Subclass Elasmobranchii Largest living sharks?Filter feeders- whale sharkPharyngeal-arch modifications that strain plankton
37Subclass Elasmobranchii Fiercest most feared sharks?Great white sharkJaws theme song on subclass! FYI the book says great white and mako? I question mako???Great White Shark (Carcharodon carcharias),South Africa, Atlantic Ocean.
38Subclass Elasmobranchii Skates and rays Life on the ocean floor in shallow waters Wing like appendages CamouflageThe little skate settles on the ocean floor where it blends in with the light colored sand. It can easily surprise any prey while waiting in this position.
39Subclass Holocephali Holo- whole, cephal-head Ratfish Lack scales Gill covered with operculumTeeth large plates for crushing
40Class Osteichthyes Osteo- bone, ichthyes- fish Bone in skeleton and/or scalesBony operculum covering the gill openingsLungs or swim bladder
41Class Osteichthyes Subclass Sarcopterygii Sacro-flesh, pteryx- fin Muscular lobes associated with finsUse lungs in gas exchange
42Subclass Sarcopterygii LungfishLive in regions where seasonal droughts are commonWhen water stagnates and dry up use lungs to breathe air
43Subclass Sarcopterygii CoelacanthsThought to be exinctBut 1938 in South Africa, found oneIn 1977 another species found off coast of IndonesiaA coelacanth swimming near Sulawesi, Indonesia
44Subclass Sarcopterygii OsteolepiformsAre extinctBelieve to be ancestors of ancient amphibians
45Subclass Actinopterygii Actin- ray, pteryx-finRay-finned fishes because their fins lack muscular lobesSwim bladder-gas-filled sacs along the dorsal wall of the body cavity that regulates buoyancySwim_bladder of a Rudd (Scardinius erythrophthalmus)
46Subclass Actinopterygii One group is called: Chondrosteans25 living species todayAncestral species had a bony skeleton but living members have a cartilaginous skeleton.Tail with a large upper lobe.
47Subclass Actinopterygii ChondrosteansSturgeonsLive in sea and migrate into rivers to breedBony plates cover the anterior of bodyValued for their eggs-caviar (severely overfished)
48Subclass Actinopterygii ChondrosteansPaddlefishesLarge, freshwaterPaddlelike rostrum- sensory organs pick up weak electrical fieldsFilter feedersLakes & rivers of the Mississippi River basin
49Subclass Actinopterygii The second group is: NeopterygiiTwo primitive genera that live in freshwaters of North America are:Garpike-thick scales long jawsDogfish or bowfinDogfish can be confused with snakeheads. . .very different though!
50Subclass Actinopterygii NeopterygiiMost living fishes that are members of this group are refered to as:Teleosts or modern bony fishesNumber of teleost species exceeds 24,000!When you think of fishes these are animals that pop into your head!
51What is the largest successful vertebrate group? Fishes
52Why are fishes so successful? Adapt to environmentExtract oxygen from small amounts of oxygen per unit volumeEfficient locomotor structuresHigh sensory systemEfficient reproduction (produces overwhelming number of offspring)
53Locomotion Stream line shape Mucoid secretions lubricates body to decrease friction between fish and waterUse fins and body wall to push against water.The muscles provide the power for swimming and constitute up to 80% of the fish itself. The muscles are arranged in multiple directions (myomeres) that allow the fish to move in any direction.
54Locomotion The trunk and tail musculature propels a fish. Muscles are arranged in zigzag bands called myomeres; they have the shape of a W on the side of the fish.Internally the bands are folded and nested; each myomere pulls on several vertebrae.Fig. 24.Fig. 24
55Nutrition and Digestion Most are predators (always searching for food)Invertebrates, vertebratesSwallow prey wholeCapture prey: suction-closing the opercula and rapidly opening mouthSome filter feeders- Gill rakers: trap plankton while the fish is swimming with mouth open.Some herbivores and omnivores
56Nutrition and Digestion Whale Sharks live in the Tropical Warm Waters all around the world. For eating, they swim quite near the water surface.A giant grouper seenswimming among schools of other fish
57Circulation and Gas Exchange The heart only has two chambersFish heart only pumps blood in one direction
58The blood enters the heart through a vein Exits through a vein on its way to the gills.In the gills, the blood picks up oxygen from the surrounding water and leaves the gills in arteries, which go to the body.The oxygen is used in the body and goes back to the heart.A very simple closed-circle circulatory system.
62Circulation and Gas Exchange The blood flows thorough the gill filaments and secondary lamellae in the opposite direction from the water passing the gills.This is very important for getting all of the available oxygen out of the water and into the blood
63The countercurrent exchange system Provides very efficient gas exchange by maintaining a concentration gradient between the blood and the water over the entire length of the capillary bed.
67Circulation and Gas Exchange How do fish ventilate their gills?Fish must pass new water over their gills continuously to keep a supply of oxygenated water available for diffusion.Fishes use two different methodsRam VentilationDouble pump system
68Ram VentilationSwim through the water and open your mouth (ram water into mouth)include the great white shark, the mako shark, the salmon shark and the whale shark , tuna
70FYIWhen fish are taken out of the water, they suffocate. This is not because they cannot breathe the oxygen available in the air, but because their gill arches collapse and there is not enough surface area for diffusion to take place. There are actually some fish that can survive out of the water, such as the walking catfish (which have modified lamellae allowing them to breathe air. It is possible for a fish to suffocate in the water. This could happen when the oxygen in the water has been used up by another biotic source such as bacteria decomposing a red tide. SEE March 8,2011
71Circulation and Gas Exchange Swim bladders-help to maintain buoyancy in the water.a sac inside the abdomen that contains gas.
724 Ways Fishes can Maintain their Vertical Position 1. Fishes are saturated with buoyant oils. (especially in liver)2. Use their fins to provide lift.3. Reduction of heavy tissues. (bones less dense, cartilaginous skeletons)4. Swim bladder.
73Nervous and Sensory Functions Has a brain and a spinal cordExternal nares – in snouts of fishes lead to olfactory receptorsSalmon and lampreys return to streams they were spawned from due to the odorsEyes – lidless with round lenses; focus by moving lens forward or backwardInner ears – equilibrium, balance, hearing (similar to other vertebrates)
74Nervous and Sensory Functions Lateral-line system – sensory pits in epidermis detect water currents (from predators) or low frequency soundsElectroreception – detection of electrical fields that the fish or another organism generatesHighly developed in the rays and sharksSharks cannot detect organisms wrapped in polyvinyl insulated sheets/bags. That’s why downed aircrafts use them.
75Nervous and Sensory Functions Electric fish – currents circulate from electric organs in fish’s tail to electroreceptors near its headan object in the field changes the patternLive in murky fresh waters in Africa or Amazon basin in South AmericaEX: electric eel (bony fish)Shocks in excess of 500 voltsEX: electric ray (an elasmobranch)Pulses of 50 volts
76Excretion and Osmoregulation Kidneys and gills- maintain proper balance of electrolytes (ions) and water in their tissuesNephrons- excretory structures in the kidneys that filter bloodborne nitrogenous waste, ions, water, and small organic compounds across a network of capillaries called: glomerulusFiltrate passes to a tubule system essential components are absorbed into blood filtrate remaining- is excreted
77Freshwater Fishes Never drink! Only take in water when eating.Numerous nephrons with LARGE glomeruli and SHORT tubule systemsLittle water reabsorbedLarge quantities of diluted urineActive transport of ions into bloodGet salt in their food
81Marine Fishes Must combat water LOSS Drink water 3.5% ions in environment 0.65% ions in tissuesDrink waterEliminate excess ions by excretions, defection, and active transport across gill.Nephrons -SMALLER glomerculi and LONGER tubule systemsWater absorbed from nephrons
85Elasmobranchs Convert nitrogenous waste into urea in the liver Urea is stored in tissues all over body (hyperosmotic to seawater)Sharks tissue is same as concentration of ions in sea waterPossess rectal gland that removes excess NaCl from blood and excretes it into the cloaca
86Diadromous Fishes Between fresh and marine environments Gills capable of coping with both uptake and secretions of ionsSalmon, lampreysSea to freshFreshwater eelFresh to sea
87Reproduction and Development Ovoparous-- Lay undeveloped eggs, External fertilization (90% of bony fish), Internal fertilization (some sharks and rays)fish lay huge numbers of eggs; a female cod may release 4-6 million eggs.Ovoviviparous- Internal development- without direct maternal nourishment-Advanced at birth (most sharks + rays)-Larval birth (some scorpeaniforms-rockfish)In fishes, oviparity is most common; the eggs are inexpensive to produce, and as eggs are in the water, they do not dry out (oxygen, nutrients are not scarce). The adult can produce many offspring, which they broadcast into the plankton column. When the offspring settle out of the plankton, they may be in totally new environments, allowing for a great area in which the young may survive. This mode also comes with its disadvantages; when born, the fish must first go through a larval stage for growth before they transform into the adult stage. In this larval stage, they must fend for themselves in obtaining food and avoiding predation. They may not find a suitable environment when they settle out of the plankton column. The survival of individual eggs is very low, so millions of eggs must be produced in order for the parent to successfully produce offspring. The other modes have their advantages, the eggs are much less prone to predation when carried within the mother, and the young are born fully advanced and ready to deal with the environment as miniature adults. These advantages come with a price-tag also; the adult must supply nutrients to its offspring and can only produce a few eggs at a time. The young are limited to the environment that their parents were in, and if this environment is deteriorating, they are stuck with it.
88Reproduction and Development Viviparous- Internal development- direct nourishment from mother-Fully advanced at birth (some sharks, surf perches)